<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <script src="./js/react.development.js"></script>
  <script src="./js/react-dom.development.js"></script>
  <title>Document</title>
</head>
<body>
  <div id="app">
    <!-- <button></button> -->
  </div>
  <script>
  //  创建元素
    let el=React.createElement(
      'button',
      {
        title:'按钮提示文字',
        className:'danger'
      },
      '提交'    
    )
    console.log(el);
    let root=document.getElementById('app')
    root = ReactDOM.createRoot(root)
    console.log(root);
    // 挂载
    root.render(el)
  </script>
</body>
</html>